20921641 has 16 divisors (see below), whose sum is σ = 24071040. Its totient is φ = 18023040.

The previous prime is 20921629. The next prime is 20921647. The reversal of 20921641 is 14612902.

It is a cyclic number.

It is not a de Polignac number, because 20921641 - 2¹¹ = 20919593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20921647) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16941 + ... + 18133.

It is an arithmetic number, because the mean of its divisors is an integer number (1504440).

Almost surely, 2^20921641 is an apocalyptic number.

It is an amenable number.

20921641 is a deficient number, since it is larger than the sum of its proper divisors (3149399).

20921641 is a wasteful number, since it uses less digits than its factorization.

20921641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1296.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 20921641 is about 4574.0180366938. The cubic root of 20921641 is about 275.5488367020.

The spelling of 20921641 in words is "twenty million, nine hundred twenty-one thousand, six hundred forty-one".